Evaluations that combine social science and law have tremendous potential to illuminate the effects of governmental policies and yield insights into how effectively policy makers' efforts achieve their aims. This potential is infrequently achieved, however, because such interdisciplinary research contains often overlooked substantive and methodological challenges. This article offers detailed guidance for conducting successful multidisciplinary evaluations that use legal data. It addresses major issues that commonly arise and offers practical solutions based both on the authors' extensive experience and recommended best practices developed in concert with the Robert Wood Johnson Foundation's Public Health Law Research Program. (Contains 1 note, 1 table, and 1 figure.)